Method and system for configuring a connection-oriented packet network over a wavelength division multiplexed optical network

ABSTRACT

A network planning tool and method for configuring a connection-oriented packet network over a WDM optical network without an optical control layer, such as a SONET/SDH layer. The optical network includes a plurality of optical fibers interconnected through nodes and the connection-oriented packet network, such an Ethernet network, MPLS network, or pseudowire network, includes two or more terminal devices. The method and tool function by building an association between the components of the physical layer, such as the optical fiber, and their geographic location or path. The connection-oriented packet network is configured by building multi-link trunks (MLTs) between terminal devices, where the MLTs are built by aggregating lightpaths that traverse distinctive geographic paths. The MLTs are planned and configured through aggregating lightpaths that traverse incongruent sets of photonic elements. A predetermined target for resiliency to physical failure events may determine the degree of congruence allowed between the sets of photonic elements associated with lightpaths in the same MLT.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 12/609,039, filed Oct. 30, 2009 and owned in common herewith.U.S. patent application Ser. No. 12/609,039 is a continuation of U.S.patent application Ser. No. 11/427,522, filed Jun. 29, 2006.

FIELD OF THE INVENTION

The present invention relates to network planning and configuration and,in particular, to the configuration of a connection-oriented packetnetwork over a wavelength division multiplexed (WDM) optical network.

BACKGROUND OF THE INVENTION

The operation and interoperation of local area networks (LAN) andmetropolitan area networks (MAN) are governed by a number of standardsdeveloped through IEEE 802, IETF and ITU Working Groups.

For example, the 802.3 Working Group develops standards related to LocalArea Networks (LAN), such as Ethernet networks.

Fiber optics are gaining wider acceptance as the media of choice forinterconnecting LANs with high capacity or serving as the backbone forMANs. The need for higher bandwidth and improvements in opticalswitching have been large factors in the increasing demand for opticalnetworks.

A typical Ethernet over optical fiber network relies upon a SONET/SDHlayer in the Metropolitan Area Network and Campus environment to providefor resiliency to hardware failures at the physical layer. The SONET/SDHlayer necessarily adds certain operational complexity to thecommunications.

Multiple Ethernet signals can be multiplexed on a single optical fiberusing wavelength division multiplexing technology (WDM). When using WDMthe signals are all assigned a unique wavelength and are allowed toshare a single optical fiber. When using WDM technology Ethernet signalsare normally encapsulated in a SONET or OTN frame. The SONET/SDH layernecessarily adds certain operational complexity to the communications.

Cost saving in terms of equipment and bandwidth may be realized byeliminating the SONET/SDH layer; however, the Ethernet layer wouldbecome vulnerable to failures at the physical layer.

The IEEE 802.3 Working Group has defined a link aggregation standard,known as IEEE 802.3ad. However, this standard is predicated on aphysical layer that supports a resilient transport network such as aSONET/SDH layer. The 802.3ad standard thus makes no provision for thefailure and resiliency attributes of a directly-connected WDM network(i.e. a WDM optical network without an optical control layer).

Accordingly, it would be advantageous to have a method for configuring aconnection-oriented packet network, like an Ethernet network, over a WDMoptical network without an optical control layer.

Moreover, the IETF MPLS Working Group develops standards related tonetworks that operate on the basis of label switch paths (LSP) thattunnel lower layer services across an internet protocol (IP) network.The IETF PWE3 Working Group develops standards for link concatenationstructures, known as pseudo-wires, that may be constructed on a varietyof network types including MPLS, IP, Ethernet and SONET networks. By wayof the methods prescribed in the IETF standards, complex layerednetworks may be configured. For example, a point-to-point Ethernetservice may be configured using pseudo-wires that exploit MPLS labelswitch routes that are themselves configured over an underlyingIP/Ethernet/transport network.

A typical MPLS network achieves resiliency by way of a underlyingrouting IP layer, or an underlying Ethernet link aggregation layer, thatthemselves achieve resiliency by way of an underlying SONET/SDH layer.The SONET/SDH layer necessarily adds certain operational complexity tothe communications and thereby reduces effective bandwidth. As indicatedabove, cost saving in terms of equipment and bandwidth may be realizedby eliminating the SONET/SDH layer at the expense of resiliency.

The IETF MPLS and pseudo-wire Working Groups have provided standardmethods for concatenating links to define routes through a network.Further, drafts submitted at IETF Working Groups have included proposalsfor an Optimized Multipath Algorithm that combines MPLS label switchpaths according to an algorithm, so as to create a structure similar tothat of an IEEE 802.3ad link aggregation structure but where the linksare LSPs instead of Ethernet links.

Accordingly, it would be advantageous to have a method for configuring aconnection-oriented packet network, like an MPLS network or a pseudowirenetwork, over a WDM optical network without an optical control layer.

More broadly, it would be advantageous to provide for a network planningtool and method that improves Ethernet, MPLS, pseudo-wire and/orOptimized Multipath Algorithm resiliency in the absence of an underlyingresilient layer.

SUMMARY OF THE INVENTION

The present invention provides a network planning tool and method forconfiguring a connection-oriented packet network over a WDM opticalnetwork in the absence of an optical control layer. In one aspect of theinvention, the tool and method provide for configuring these networks tomeet a predetermined resiliency target.

The optical network comprises a photonic layer that includes a pluralityof photonic elements, like optical fibers, interconnected through nodes,and the Ethernet network includes two or more Ethernet switches.

The components of the photonic layer may include fiber conduits, fiberbundles, optical fibers, fiber patch panels, optical multiplexers,optical filters, optical amplifiers, photonic switches, reconfigurableoptical add/drop multiplexers, WDM regenerators, WDM wavelengthtranslators, WDM electro-optic interface devices, and assemblies ofthese elements. The method and tool may function so as to build anassociation between the elements of the photonic layer and theirgeographic locus or path. Those components that share the samegeographic loci may be noted.

The photonic layer is used by the WDM layer. The components of the WDMlayer are defined in terms of lightpaths. The method and tool mayfunction so as to build an association between a lightpath and the lociof the photonic layer components that are used by the lightpath.

The WDM layer is used by the connection-oriented packet layer, such asan Ethernet layer. The connection-oriented packet network is configuredby building multi-link trunks (MLTs) between terminal devices, likeEthernet switches, where the MLTs are built by aggregating two or morelinks, wherein each link comprises one or more concatenated lightpaths.The method and tool may function so as to aggregate links to an MLThaving regard for the respective geographic loci associated with thelightpaths that make up the links. The method and tool may be used toensure the MLTs are planned and built such that a first link and asecond link in the MLT do not share a common geographic path. In oneembodiment, the MLT may include links that use respective sets ofphysical layer components where the sets are completely disjoint orwhere the sets intersect to a minimal extent that meets a predeterminedresiliency target. In other words, the MLT can be configured to providethe connection-oriented packet network with topological diversity and,therefore, meet a predetermined target for resiliency to physicalfailure events.

It should be understood that an MLT in this invention may, in someembodiments, be a link aggregation structure as defined in IEEE 802.3ad,or an Optimized Multipath Algorithm label switch path structure asdescribed in IETF drafts, or any other structure of parallel logicallinks.

In one aspect, the present invention provides a method of configuring aconnection-oriented packet network over a wavelength divisionmultiplexed (WDM) optical network without an optical control layer. TheWDM network includes a first terminal device and a second terminaldevice, and each terminal device includes WDM electro-optic interfaces.The WDM network has a photonic layer connecting the WDM electro-opticinterfaces, and the photonic layer includes a plurality of photoniclayer elements including optical fibers. The photonic layer provides aplurality of lightpaths between the terminal devices, and each lightpathtraverses a set of the photonic layer elements. The method includes thesteps of associating a geographic loci with each of the photonic layerelements, defining a multilink trunk between the first terminal deviceand the second terminal device, and selecting a first lightpath toaggregate to the multilink trunk. The first lightpath traverses a firstset of the photonic layer elements, and the first set of photonic layerelements has a first set of associated geographic loci. The method alsoincludes a step of selecting a second lightpath to aggregate to themultilink trunk. The second lightpath traverses a second set of thephotonic layer elements, and the second set of photonic layer elementshas a second set of associated geographic loci. The step of selectingthe second lightpath includes selecting the second lightpath on thebasis that the second set of geographic loci is incongruent with thefirst set of geographic loci.

In another aspect, the present invention provides a computer-implementednetwork planning tool for configuring a connection-oriented packetnetwork over a wavelength division multiplexed (WDM) optical networkwithout an optical control layer. The planning tool includes a computerreadable medium storing computer executable instructions. The WDMnetwork includes a first terminal device and a second terminal device,and each terminal device includes WDM electro-optic interfaces. The WDMnetwork has a photonic layer connecting the WDM electro-opticinterfaces, and the photonic layer includes a plurality of photoniclayer elements including optical fibers. The photonic layer provides aplurality of lightpaths between the terminal devices, and each lightpathtraverses a set of the photonic layer elements. The computer executableinstructions include computer executable instructions for associating ageographic loci with each of the photonic layer elements, computerexecutable instructions for defining a multilink trunk between the firstterminal device and the second terminal device, and computer executableinstructions for selecting a first lightpath to aggregate to themultilink trunk. The first lightpath traverses a first set of thephotonic layer elements, and the first set of photonic layer elementshas a first set of associated geographic loci. The network planning toolalso includes computer executable instructions for identifying a secondlightpath to aggregate to the multilink trunk. The second lightpathtraverses a second set of the photonic layer elements, and the secondset of photonic layer elements has a second set of associated geographicloci. The computer executable instructions for identifying the secondlightpath perform identification of the second lightpath on the basisthat the second set of geographic loci is incongruent with the first setof geographic loci.

Other aspects and features of the present invention will be apparent tothose of ordinary skill in the art from a review of the followingdetailed description when considered in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be made, by way of example, to the accompanyingdrawings which show one or more embodiments of the present invention,and in which:

FIG. 1 diagrammatically shows a known networking architecture model forEthernet over optical networks;

FIG. 2 diagrammatically shows a second networking architecture model forEthernet over optical networks;

FIG. 3 diagrammatically shows a networking architecture model for MPLSover IP over Ethernet over optical networks;

FIG. 4 shows, in block diagram form, a portion of a network inaccordance with the present application;

FIG. 5 shows one embodiment of an example photonic network;

FIG. 6 shows the geographic paths of a logical link within the examplephotonic network of FIG. 5;

FIG. 7 shows, in diagrammatic form, an example user interface ofinter-layer network planning tool; and

FIG. 8 shows, in flowchart form, an embodiment of a method forconfiguring an Ethernet network over a WDM optical network.

Similar reference numerals are used in different figures to denotesimilar components.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Reference is first made to FIG. 1, which diagrammatically shows a knownnetworking architecture model 10 for Ethernet over optical networks. Themodel 10 is a conventional configuration in which an Ethernet layer 12operates over an optical layer 14, which in this example is a SONET/SDHlayer. As used in this description, an optical layer refers to a layerwhere the signals from the Ethernet switch are captured by a specializedelectronic system which manages banks of WDM transponders. Theelectronic system directs the signal to a predetermined wavelength,through a transponder on the photonic layer and will switch thewavelength and direction on the ring in the advent of a failure. Theoptical layer 14 in turn operates over the physical photonic layer 16.The physical photonic layer 16 may employ Wavelength DivisionMultiplexing (WDM) data transport, which may by configured as DenseWavelength Division Multiplexing (DWDM), Course Wavelength DivisionMultiplexing (CWDM), or Sparse Wavelength Division Multiplexing (SWDM).

Reference is now made to FIG. 2, which shows a second networkingarchitecture model 20, proposed in accordance with the presentapplication. The second model 20 includes the Ethernet layer 12, buteliminates the optical (SONET/SDH) layer 14 (FIG. 1). In other words, inthe second model 20, the Ethernet layer 12 operates directly over thephotonic layer 16, thereby eliminating the operational complexityassociated with the SONET/SDH layer 14. It will be noted that Ethernetaggregation 11 is performed at the Ethernet layer 12. The Ethernetaggregation 11 aspect includes the defining of multilink trunks to formthe Ethernet network, as will be explained in greater detail below.

The difficulty associated with eliminating the SONET/SDH layer 14 isthat this layer provides certain resiliency features. For example, theSONET/SDH layer 14 typically uses a ring topology with a SONET-definedprotocol for identifying failures and coordinating recovery in the eventof a failure at one point on the ring. The Ethernet layer 12 typicallyhas no knowledge of the underlying physical topology and relies upon theSONET/SDH layer 14 to manage recovery from physical network failures. Ifthe SONET/SDH layer 14 is removed, then the network improves itsoverhead but loses its resiliency.

Accordingly, in one aspect, the present application provides a method ofconfiguring an Ethernet network over a WDM photonic network so as toimprove resiliency.

To provide a further example, reference is now made to FIG. 3, whichshows a networking architecture model 22 for MPLS over IP, overEthernet, over a WDM photonic network. From the model 22, it will benoted that a label switch path layer 26 operates over an IP layer 24,which in turn operates over the Ethernet layer 12. The Ethernet layer 12runs directly atop the photonic layer 16. A pseudowire layer 28 may beprovided above the label switch path layer 26. The label switch pathlayer 26 may include label switch path aggregation 25 for formingmultilink trunks, as will be described in greater detail below. It willbe noted that the various connection-oriented packet layers operate atopthe photonic layer 16 without an intermediate optical layer 14 (FIG. 1)such as SONET/SDH.

Those skilled in the art will recognize that various other networkingarchitecture models may be realized, including various combinations ofEthernet, IP, MPLS, and/or pseudowire layers.

Reference is now made to FIG. 4, which shows, in block diagram form, aportion of a network 30 in accordance with the present application. Thenetwork 30 includes a WDM layer 32, which includes optical fiber,optical routers, switches, and other photonic layer equipment. Thenetwork 30 also includes a plurality of Ethernet switches 34 or hubs(one shown), where the switch 34 or hub includes integrated DWDMpluggable optical transceivers 36 (one shown).

By putting the DWDM interface directly into the Ethernet switch 34, theresult is that lightpaths terminate at layer 2 nodes. In other words,there is a mapping between Ethernet ports and lightpaths; interlayerbinding makes the photonics a function of the data link layer, insteadof the data link layer riding on top of a photonic layer.

Reference is now made to FIG. 5, which shows one embodiment of anexample photonic network 100. The photonic network 100 is configured asa fiber ring 102 for the simplicity of illustration, although thoseskilled in the art will appreciate that other topologies are possible.

The fiber ring 102 includes one or more optical fibers 104 each carryinga plurality of wavelengths. Typically, the fiber ring 102 may include atleast two optical fibers 104, one for transmissions clockwise, the otherfor transmission counterclockwise around the ring, although the presentapplication is not limited to this embodiment.

The fiber ring 102 includes a plurality of photonic elements, such asnodes 106 (shown individually as 106 a, 106 b, 106 c, 106 d). The nodes106 may be optical WDM MUX/DMUX equipment. Simple nodes could beemployed where a simple filter is used to remove and add wavelengths onthe photonic ring. In some embodiments, the nodes 106 may include aphotonic cross-connect switch for directing wavelength to desired outputports, wavelength translators could also be used for changingwavelengths. Those skilled in the art will appreciate the breadth ofpossible implementations of the nodes 106.

The optical network 100 is accessed by Ethernet switches 110 (shownindividually as 110 a, 110 b, 110 c, and 110 d). Each Ethernet switch110 connects to the fiber ring 102 through one of the nodes 106 on thefiber ring 102. The Ethernet switches 110 include DWDM opticaltransceivers. In particular, the Ethernet switches 110 include a DWDMoptical transceiver for sending and receiving a specific wavelength foreach “port” on the Ethernet switch 110. The designated node 106 for agiven Ethernet switch 110 manages the insertion or adding onto the fiberring 102 of wavelengths transmitted by the given Ethernet switch 106 andmanages the removal or dropping of wavelengths for reception by thegiven Ethernet switch 106. The methods and equipment for adding anddropping of wavelengths in an optical node will be understood by thoseof ordinary skill in the art. An example embodiment of such an opticalnode is described in US patent publication no. 2002/0126334A1, publishedSep. 12, 2002, and owned in common herewith.

An Ethernet network is established over the photonic network 100. TheEthernet network is configured to include logical links 120 (shownindividually as 120 a, 120 b, 120 c) between the switches 110. In thepresent embodiment, the Ethernet switch 110 a is connected to anapplication host or server, and the Ethernet switch 110 a therefore actsas a hub of the Ethernet network. Ethernet switches 110 b, 110 c, and110 d are connected to client devices or other networks containingclient devices. The Ethernet-level logical link connections 120 a, 120b, 120 c between the Ethernet switches 110 are shown in dashed lines. Itwill be appreciated that the description of the present embodiment doesnot limit the scope of possible embodiments to hub and spokearchitecture.

IEEE Standard 802.3-2002 defines certain characteristics and behaviorsapplicable to Ethernet-type networks. Clause 43 of the standard(introduced by way of IEEE 802.3ad) describes the possibility of linkaggregation and the use of an optional link aggregation sublayer.Aggregation is used to allow a MAC client to communicate using multiplepaths/links where the fact of the multiple paths/links is invisible tothe MAC Client. An Aggregator presents a single interface to the MACclient and manages the parsing and multiplexing associated withtransmitting and receiving data through multiple ports. Multiple linksaggregated together may be referred to as a Multi-link Trunk (MLT).

In accordance with the present application, MLTs are used to establishthe Ethernet network over the optical network 100 so as to address theloss of resiliency due to the absence of a SONET/SDH or optical layer.In particular, the MLTs are built over WDM based upon the aggregation oftwo or more lightpaths connecting two nodes 106. Where FIG. 5 depicts anMLT using a pair of dashed lines, it will be appreciated that eachdashed line is intended to represent two lightpaths. One lightpathallows for transmission and reception in one direction, and the otherlightpath allows for transmission and reception in the other direction,thereby collectively providing full-duplex operation between a pair ofEthernet switches 110. It will be appreciated that each MLT includes atleast four lightpaths and, therefore, two full-duplex transmissionlinks.

Those skilled in the art will appreciate that the term “lightpath” isused to describe a point-to-point all optical wavelength-level channelbetween a transmitter at one of the Ethernet switches 110 and a receiverat another of the Ethernet switches 110 in a logical link. Although inmany cases a lightpath may be established over a single wavelength,those skilled in the art will appreciated that in some embodiments alink may traverse a node or switch that causes the link to be switchedto a different wavelength. For this reason, the term “lightpath” is usedto describe the constituent elements of an MLT, although it will beunderstood that at any one physical point along its path a “lightpath”is a single wavelength. In some embodiments, a link between two Ethernetswitches 110 may include two or more concatenated lightpaths.

In configuring the Ethernet network by establishing the MLTs, the two ormore lightpaths are selected for aggregation to the MLT such that theyprovide resiliency in the case of physical failure. In particular, thetwo or more lightpaths are selected such that they have a distinctivegeographic path. In other words, the second lightpath added to an MLTshould travel a different physical path using different photonicelements than the first lightpath.

To configure the Ethernet network or, in particular, aggregatelightpaths to form an MLT and achieve geographic distinctiveness, aconcept of geographic loci or physical location—i.e. of the physicallayer—is required at the Ethernet layer. In other words, the layer 2planning or configuring operation makes use of knowledge regarding thephysical layer. The use of concepts of lightpath, photonic elements, andgeography (i.e. level 0) at the level of Ethernet layout (i.e. level 2)logical link planning may be referred to as ‘interlayer binding’.

By way of example, reference is now made to FIG. 6, which shows thegeographic paths of one of the logical links 120 a in the opticalnetwork 100 of FIG. 5. The four sections of optical fiber 104 formingthe fiber ring 102 travel distinctive geographic paths. The logical link120 a set up between Ethernet switch 110 a and Ethernet switch 110 dincludes at least two pair of lightpaths, a first lightpath pair 120 a-1and a second lightpath pair 120 a-2, having distinctive geographicpaths. In particular, the first lightpath pair 120 a-1 traverses thesegment of the fiber ring 102 between nodes 106 a and 106 d. The secondlightpath pair 120 a-2 added to the MLT for logical link 120 a is chosento have a different geographic path. Accordingly, the second lightpathpair 120 a-2 is selected such that it traverses the other sections ofthe fiber ring 102 passing through nodes 106 b and 106 c. In thismanner, if a physical failure occurs at any one point on the ring 102,such as a cut optical fiber 104, the MLT provides resiliency by offeringa different geographic path.

The standard of a distinctive geographic path may, in one embodiment, berealized as distinctive optical fiber. It will be appreciated that, insome instances this may result in lightpaths in the same physical space,since fibers may be bundled in a conduit and travel the same route. Inanother embodiment, the standard may be realized as distinctiveconduits, meaning that even when the lightpaths travel in differentfibers, the fibers cannot be co-located in a common physical conduit. Inyet another embodiment, the standard may be realized as distinctiveoptical equipment, meaning that intermediate nodes, amplifiers, etc.,are not shared by the lightpaths. In yet other embodiments, anassociation may be made between lightpaths and geographic markers, suchas GPS coordinates, street names, etc., and geographic distinctivenessmay be realized through ensuring distinctive geographic markers. Otherembodiments may realize application of the standard of ‘distinctivegeographic path’ in other manners, including combinations of theabove-described factors.

In one embodiment, each photonic element is associated with a geographicloci, including optical fibers, nodes, switches, etc., and eachlightpath is recognized as existing over a set of photonic elements. Forexample, with reference to FIG. 6, the first pair of lightpaths 120 a-1is established over a set of photonic elements that includes node 106 a,node 106 d, and an optical fibre 104 between node 106 a and node 106 d.The second lightpath pair 120 a-2 is established over a set of photonicelements that includes all four nodes 106, and an optical fiber 104between node 106 a and node 106 d, an optical fiber between node 106 band node 106 c, and an optical fiber between node 106 c and node 106 d.Accordingly, the set of photonic elements supporting the secondlightpath pair 120 a-2 have geographic loci that are incongruent(although not entirely distinctive because of the common nodes 106 a and106 d) with the geographic loci of the set of photonic elementssupporting the first lightpath pair 120 a-1. The lightpaths 120 atherefore have a certain level of geographic distinctiveness. It will beappreciated that in a more complex network structure, various candidatelightpaths may present varying degrees of geographic distinctivenessfrom one another, thereby allowing for selection of two lightpathshaving at least a minimal degree of geographic distinctiveness. In oneembodiment, the candidate lightpaths may be selected on the basis thatthey have the greatest degree of geographic distinctiveness (i.e. thegreatest degree of incongruence between their respective sets ofphotonic elements).

Reference is now made to FIG. 7 which illustrates, in diagrammatic form,an example user interface of inter-layer network planning tool. FIG. 7includes two network views: a physical layer view 200 and an opticalEthernet layer view 202.

From the physical layer view 200, it will be noted that the opticalnetwork 100 includes six Ethernet switches 110 interconnected by thefiber ring 102 through a plurality of nodes (shown broken down into aplurality of MUX/DEMUX elements 108, e.g. two such elements 108 pernode). The individual hops between elements are shown with a numberindicating the quantity of distinct wavelengths that make up the hop.These wavelengths may be distinctive wavelengths in the same fiber orsome of them may be the same wavelengths in two or more optical fibers.The connections between the Hub Ethernet switch 110-1 and its associatedMUXs 108-1, 108-2 are shown with distinctive lines for each wavelengthto illustrate the number of wavelengths that make up the connection.

It will be noted that at many of the nodes along the fiber ring 102 awavelength is removed and a wavelength is added by a MUX/DEMUX pair ofelements 108 for the connection to the corresponding Ethernet switch110.

The optical Ethernet layer view 202 shows the hub Ethernet switch 110-1and MLTs 220 connecting the hub Ethernet switch 110-1 to each of theother Ethernet switches 110. The MLTs 220 include at least twolightpaths pair. The MLT 220-1 between the hub Ethernet switch 110-1 andEthernet switch 110-2 includes three lightpaths pair.

Each MLT 220 includes at least a first lightpath pair and a secondlightpath pair traversing geographically diverse paths. In assemblingthe MLT by aggregating individual lightpaths to the MLT, the graphicaluser interface may present candidate lightpaths in the physical layerview for selection by a user. For example, it may provide a picklist ofthe candidate lightpaths, which may be uniquely labeled or otherwiseidentified. In one example embodiment, candidate lightpaths may behighlighted in the physical layer view. As shown in FIG. 4, if alightpath is selected in the optical Ethernet view, the physical layerview may highlight the geographic path traversed by the selectedlightpath. This feature may assist the network designer/planner invisually identifying physically divergent lightpaths to ensure that theMLT contains at least two lightpaths pair traveling distinctivegeographic paths. The MLTs may then be built from aggregating lightpathsusing the principle that at least one lightpath pair in the MLT shouldhave a distinctive geographic path from at least one other lightpathpair in the MLT. The decision as to how much geographical diversity isrequired may be taken into account by the planner depending on theservice agreement and the required resiliency.

Reference is now made to FIG. 8, which shows, in flowchart form, anembodiment of a method 300 for configuring an Ethernet network over aWDM optical network. The method 300 may, in one embodiment, be embodiedin a network planning tool implemented in software stored in on acomputer readable medium and providing instructions for execution by theprocessor of a general purpose computer in known manner. The softwaremay generate a graphical user interface in known manner to displayinformation to a user and solicit and receive user input in accordancewith the method 300. The suitable programming of such software will bewithin the understanding of a person of ordinary skill in the art havingregard to the description herein.

The method 300 begins in step 302 with the establishment of the physicallayer. This step 302 includes the design of the physical layer opticalnetwork, such as the selection of Ethernet switches, nodes, fiber links,and other physical plant. Portions of this step 302 may be performedoff-line. The step 302 in a computer-implemented embodiment of themethod 300 may include the selection of constituent physical elements ofthe optical network and the placement of those elements in a physicalnetwork view on the graphical user interface. For example, switches,nodes, and such discrete elements may be represented by graphical icons.The user may be prompted to name or label each new item. Fiber links maybe established between distinct elements. Distances and other physicaldetails regarding the optical network may be input by the user. Thegraphical user interface may provide the user with a graphical image ofthe selected and assembled physical layer network, such as that shown inFIG. 3 or FIG. 4.

In step 304, associations are made between the physical elements of thephysical layer and geography. In particular, each optical fiber, orwavelength, may be assigned a geographical loci or indicator relatingthereto.

In one embodiment, the associations may be made by selecting co-locatedelements, such as two fibers sharing a common path, and choosing todesignate the selected elements as being geographically indistinct. Inanother embodiment, the concept of a “conduit” or other common path maybe provided within the physical layer view, thereby allowing a user toindicate when two fibers share the same geographic path. In yet anotherembodiment, each element is associated with a geographic indicator orlabel. Those elements having a common location or path may share acommon geographic indicator or label.

Once associations are made between the physical elements at the physicallayer and geographical location, then in step 306 of the method 300 theuser may begin to configure the Ethernet network by developing linksbetween Ethernet elements, such as the Ethernet switches. In particular,in step 306, the user may choose to connect two Ethernet elements (i.e.switches) by way of an MLT.

In step 308, a first lightpath is aggregated added to the MLT. In someembodiments, the user may be presented with a picklist of possiblecandidate lightpaths based upon the physical layer structure,availability and the user's selection of the two Ethernet switches to beconnected. In other embodiments, the user may build a lightpath betweenthe two Ethernet switches through selecting (for example, using a mouseor other input device) individual wavelengths on individual hops betweenthe two Ethernet switches. In the latter case, the software mayrationalize wavelength selections to minimize the number of wavelengthchanges at any cross-connect switches.

Based upon the aggregation of the first lightpath to the MLT, in step310 the available lightpaths having a distinctive geographic path may beidentified. A candidate lightpath may be identified on the basis that ithas a geographic path distinct from the geographic path associated withthe first lightpath aggregated to the MLT. In an embodiment wherein theassociations between geography and optical fibers are made by way ofgroupings of commonly located elements, then the available candidatelightpaths may be identified on the basis that they (or their associatedphotonic elements) are not grouped with the first lightpath (or itsassociated photonic elements) as sharing a geographic path or loci. Inan embodiment wherein each lightpath or phonotic element is given ageographic indicator or label associated with its path, then theidentification of geographically distinctive lightpaths may be made onthe basis of a comparison of labels or indicators to identifydistinctive ones. In one embodiment, the candidate lightpaths having adistinctive geographic path from the first lightpath may be highlightedin the physical layer view of the graphical user interface or may bepresented to the user in a picklist for ease of selection.

In step 312, the user may aggregate a further lightpath to the MLT. Thefurther lightpath may be selected in the same manner as the firstlightpath. In one embodiment, the further lightpath may only be one ofthe candidate lightpaths identified in step 310 and if no suchlightpaths exist, then the user may be presented with a messageindicating the resiliency problem with the network design. In anotherembodiment, the further lightpath may or may not be one of the candidatelightpaths identified in step 310. If the further lightpath is notgeographically distinct, then in step 314 the user may be presented witha message or alert to signify that the MLT does not yet provideresiliency. This may prompt the user to delete the non-distinctivelightpath, alter the physical plant, and/or add additional lightpaths tothe MLT as indicated in step 316, or ignore the message if the user doesnot require resiliency. At step 316, the user has the option of addingmore lightpaths to the MLT, in which case the method 300 cycles back tostep 310. It will be appreciated that in some instances nogeographically distinct lightpaths may exist for an MLT having one ormore lightpaths already aggregated. In this case, a caution message maybe provided to warn the user that any further lightpaths will addcapacity, but may not significantly improve resiliency.

If the user is satisfied with the MLT created in steps 306-314, then themethod 300 continues to step 318 where the user may be permitted to adda further MLT to the Ethernet network. In this case, the method 300returns to step 306 to repeat the process for the new MLT. Otherwise, itcontinues to step 320 where the user may have the option of altering thephysical optical network. For example, having attempted to configure theEthernet network and having discovered that there are an insufficientnumber of wavelengths available, or an insufficiently geographicallydistinctive layout, the user may elect to redefine the physical plant.For example, the user may determine it is necessary to add wavelengthcapacity to the network by adding a fiber.

If the user is satisfied with the Ethernet network, then the method 300ends with step 322 whereupon the configuration information regarding theMLTs and their constituent lightpaths is output. It will be appreciatethat the output may include saving the data to a file on a computerreadable memory, sending the data to a remote computer as a message orfile, printing the data, displaying the data, etc. The configurationinformation output may include port and wavelength connectioninformation in sufficient detail to guide a technician to configure theoptical equipment in accordance with the design. The configurationinformation output may include port and wavelength connectioninformation in sufficient detail to provide a management system withenough information to trigger automatic reconfiguration of the opticalnodes and other components of the photonic network.

Those skilled in the art will appreciate that the above-described method300 may, in some embodiments, be modified such that certain steps areadded or eliminated or certain described steps are performed in adifferent sequence or are performed concurrently with other steps. Thescope and range of changes that may be made without impacting theoverall operation of the method 300 will be understood by those skilledin the art.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential characteristics thereof. Certainadaptations and modifications of the invention will be obvious to thoseskilled in the art. Therefore, the above discussed embodiments areconsidered to be illustrative and not restrictive, the scope of theinvention being indicated by the appended claims rather than theforegoing description, and all changes which come within the meaning andrange of equivalency of the claims are therefore intended to be embracedtherein.

What is claimed is:
 1. A network planning tool for configuring at leastone Ethernet Multi-Link Trunk over a wavelength-division-multiplexed(WDM) optical network, the network planning tool comprising: at leastone processor; and at least one storage medium, the storage medium beingconfigured to store instructions executable by the processor, theinstructions comprising: instructions executable to access configurationinformation for the WDM optical network, the configuration informationcomprising: geographic location information for photonic layer elementsof the WDM optical network; and available lightpaths between specifiedterminal devices connected to the WDM optical network; and instructionsexecutable to display the available lightpaths between the specifiedterminal devices connected to the WDM optical network together withgeographic location information associated with each of the availablelightpaths; and instructions executable to enable selection of one ofthe available lightpaths for aggregation as a link of an EthernetMulti-Link Trunk between the specified terminal devices connected to theWDM optical network.
 2. A network planning tool as defined in claim 1,wherein the instructions executable to display the available lightpathscomprise instructions executable to display a picklist of the availablelightpaths between the specified terminal devices.
 3. A network planningtool as defined in claim 2, wherein the instructions executable todisplay the available lightpaths comprise instructions executable todisplay geographic location information associated with each of theavailable lightpaths on the picklist.
 4. A network planning tool asdefined in claim 2, wherein the instructions executable to display theavailable lightpaths comprise instructions executable to display theavailable lightpaths in groups, each group corresponding to a respectivegeographic path.
 5. A network planning tool as defined in claim 1,wherein the instructions executable to display the available lightpathscomprise instructions executable to display a physical layer view of theWDM optical network, the physical layer view including geographiclocation information for photonic layer elements on the availablelightpaths.
 6. A network planning tool as defined in claim 5, whereinthe instructions executable to display the available lightpaths compriseinstructions for labeling lightpaths displayed in the physical layerview according to their availability.
 7. A network planning tool asdefined in claim 5, wherein the instructions executable to display theavailable lightpaths comprise instructions for highlighting lightpathsdisplayed in the physical layer view according to their availability. 8.A network planning tool as defined in claim 5, wherein the storagemedium is operable to store instructions executable to display anoptical Ethernet view of the WDM optical network.
 9. A network planningtool as defined in claim 8, wherein the storage medium is operable tostore instructions for highlighting a selected lightpath in the physicallayer view when that lightpath is selected in the optical Ethernet view.10. A network planning tool as defined in claim 1, wherein the storagemedium is further to store: instructions executable to determine whethera particular lightpath selected for aggregation as a link of theEthernet Multi-Link Trunk between the specified terminal devicesconnected to the WDM optical network is geographically diverse withrespect to other lightpaths previously selected for aggregation as linksof the Ethernet Multi-Link Trunk; and instructions executable to providean indication when the particular lightpath selected for aggregation asa link of the Ethernet Multi-Link Trunk is not geographically diversewith respect to other lightpaths previously selected for aggregation aslinks of that the Ethernet Multi-Link Trunk.
 11. A method of operating anetwork planning tool for configuring at least one Ethernet Multi-LinkTrunk over a wavelength-division-multiplexed (WDM) optical network, themethod comprising: displaying available lightpaths between specifiedterminal devices connected to the WDM optical network together withgeographic location information associated with each of the availablelightpaths based on stored configuration information for the WDM opticalnetwork, the configuration information comprising: geographic locationinformation for photonic layer elements of the WDM optical network; andavailable lightpaths between the specified terminal devices connected tothe WDM optical network; and enabling selection of one of the availablelightpaths for aggregation as a link of an Ethernet Multi-Link Trunkbetween the specified terminal devices connected to the WDM opticalnetwork.
 12. A method as defined in claim 11, wherein the displaying theavailable lightpaths comprises displaying a picklist of the availablelightpaths between the specified terminal devices.
 13. A method asdefined in claim 12, wherein the displaying the available lightpathscomprises displaying geographic location information associated witheach of the available lightpaths on the picklist.
 14. A method asdefined in claim 12, wherein the displaying the available lightpathscomprises displaying the available lightpaths in groups, each groupcorresponding to a respective geographic path.
 15. A method as definedin claim 11, wherein the displaying the available lightpaths comprisesdisplaying a physical layer view of the WDM optical network, thephysical layer view including geographic location information forphotonic layer elements on the available lightpaths.
 16. A method asdefined in claim 15, wherein the displaying the available lightpathscomprises labeling lightpaths displayed in the physical layer viewaccording to their availability.
 17. A method as defined in claim 15,wherein the displaying the available lightpaths comprises highlightinglightpaths displayed in the physical layer view according to theiravailability.
 18. A method as defined in claim 15, further comprisingdisplaying an optical Ethernet view of the WDM optical network.
 19. Amethod as defined in claim 18, further comprising highlighting aselected lightpath in the physical layer view when that lightpath isselected in the optical Ethernet view.
 20. A method as defined in claim11, further comprising: determining whether a particular lightpathselected for aggregation as a link of the Ethernet Multi-Link Trunkbetween the specified terminal devices connected to the WDM opticalnetwork is geographically diverse with respect to other lightpathspreviously selected for aggregation as links of the Ethernet Multi-LinkTrunk; and providing an indication when the particular lightpathselected for aggregation as a link of the Ethernet Multi-Link Trunk isnot geographically diverse with respect to other lightpaths previouslyselected for aggregation as links of the Ethernet Multi-Link Trunk. 21.A non-transitory processor-readable medium for use in a network planningtool, the medium carrying instructions executable by a processor, theinstructions comprising: instructions executable to access configurationinformation for a wavelength-division-multiplexed (WDM) optical network,the configuration information comprising: geographic locationinformation for photonic layer elements of the WDM optical network; andavailable lightpaths between specified terminal devices connected to theWDM optical network; instructions executable to display the availablelightpaths between the specified terminal devices connected to the WDMoptical network together with geographic location information associatedwith each of the available lightpaths; and instructions executable toenable selection of one of the available lightpaths for aggregation as alink of an Ethernet Multi-Link Trunk between the specified terminaldevices connected to the WDM optical network.
 22. A processor-readablemedium as defined in claim 21, wherein the instructions executable todisplay the available lightpaths comprise instructions executable todisplay a picklist of the available lightpaths between the specifiedterminal devices.
 23. A processor-readable medium as defined in claim22, wherein the instructions executable to display the availablelightpaths comprise instructions executable to display geographiclocation information associated with each of the available lightpaths onthe picklist.
 24. A processor-readable medium as defined in claim 22,wherein the instructions executable to display the available lightpathscomprise instructions executable to display the available lightpaths ingroups, each group corresponding to a respective geographic path.
 25. Aprocessor-readable medium as defined in claim 21, wherein theinstructions executable to display the available lightpaths compriseinstructions executable to display a physical layer view of the WDMoptical network, the physical layer view including geographic locationinformation for photonic layer elements on the available lightpaths. 26.A processor-readable medium as defined in claim 25, wherein theinstructions executable to display the available lightpaths compriseinstructions for labeling lightpaths displayed in the physical layerview according to their availability.
 27. A processor-readable medium asdefined in claim 25, wherein the instructions executable to display theavailable lightpaths comprise instructions for highlighting lightpathsdisplayed in the physical layer view according to their availability.28. A processor-readable medium as defined in claim 25, wherein thestorage medium stores instructions executable to display an opticalEthernet view of the WDM optical network.
 29. A processor-readablemedium as defined in claim 28, wherein the storage medium storesinstructions for highlighting a selected lightpath in the physical layerview when that lightpath is selected in the optical Ethernet view.
 30. Aprocessor-readable medium as defined in claim 21, wherein the storagemedium stores: instructions executable to determine whether a particularlightpath selected for aggregation as a link of the Ethernet Multi-LinkTrunk between the specified terminal devices connected to the WDMoptical network is geographically diverse with respect to otherlightpaths previously selected for aggregation as links of the EthernetMulti-Link Trunk; and instructions executable to provide an indicationwhen the particular lightpath selected for aggregation as a link of theEthernet Multi-Link Trunk is not geographically diverse with respect toother lightpaths previously selected for aggregation as links of theEthernet Multi-Link Trunk.